The present invention relates to an encoded symbol reader used to decode encoded symbols such as two dimensional tessellated codes.
Recently, point-of-sale systems have employed encoded symbol readers in order to scan bar-code labels on products, increase the speed at which products to can be processed through a check-out line of a store. However, bar-code labels store data in only one direction (i.e., the scanning direction) and, therefore can only store a limited amount of data.
To overcome the problem of limited data storage, a new type of symbol which stores data in two directions has been proposed. This new type of symbol (hereinafter referred to as a two-dimensional symbol) uses a tessellated pattern to store the data.
However, when reading the encoded symbol, the brightness of the image of the encoded symbol received must be adjusted to be within a predetermined range, if the symbol is to be decoded properly. The adjustment of the brightness is achieved, for example, by changing an integration time period of a reader such as a CCD (charge coupled device) and compensating the read brightness values using predetermined reference values stored in a memory. However, depending on the ambient light conditions and a material on which the code is printed, the stored reference values may not sufficiently compensate the read brightness values, and the symbol may not be properly decoded.